SMCP Rewrite: FastMCP to Base MCP Library — and 100% Test Pass Rate

Why Rewrite?

SMCP (Sanctum Model Context Protocol Server) was originally built on FastMCP. That worked, but it added a dependency layer between Sanctum and the MCP specification itself. As the MCP ecosystem matured — Anthropic's open protocol for connecting AI agents to external tools and data — it became clear that building directly on the base MCP library would give us tighter control over transport (SSE vs. Streamable HTTP), better compatibility with upstream clients, and a cleaner plugin discovery story.

What Changed

The complete rewrite touches nearly every file in the repo:

• Transport: Reverted to SSE for proper MCP client compatibility after discovering streamable HTTP didn't handshake cleanly with all clients.
• Plugin discovery: Plugins are now found via environment variable paths, and each plugin supports --describe for introspection (resolving GitHub issues #5 and #7).
• Security: Default binding switched to 127.0.0.1 (localhost-only). You opt in to network exposure, not out.
• Packaging: Proper console_script entrypoints, requirements.txt, and MCP_HOST env var support.

The Test Marathon

Between October 10–11, the test suite went from first-E2E-passing to 100% pass rate in a focused sprint: managed server lifecycle for integration tests, semantic tool annotations, and comprehensive packaging config. The commit log reads like a victory lap — because it is one.

Branding Note: Animus and Sanctum

You'll see references to "Animus Letta MCP Server" in the commit history. Animus is a sister project to SanctumOS focused on sovereign autonomous machines — think embodied AI agents and robotics. The two projects share architectural DNA, including parallel forks of SMCP, Cochlea, and Thalamus. During the rewrite, some commits carried the Animus branding; SMCP remains the canonical name in the Sanctum ecosystem going forward.